The present invention relates to a device for fusing optical fibers using an arc discharge.
A conventional automatic optical fiber fusing device will be described with reference to FIG. 1. In FIG. 1, reference numerals 1 and 1' designate optical fibers, 2 and 2' fiber supporting stands adapted to support optical fibers from the end portions of which the covers have been removed, 3 and 3' stands adapted to fix or hold the fibers through the covers, 4 a reference element for determining the initial distance between the ends of the fibers, 5 a compression spring, 6 a micrometer head, 7 and 7' gears, and 8 an electric motor.
In operation, first the fibers from the end portions of which the covers have been removed are placed on the fiber supporting stands 2 and 2' and are then slid axially until the ends of the fibers abut against the reference element 4. Thereafter, the optical fibers are attached through the covers to the holding stands 3 and 3'. The electrodes used for creating the arc discharge for fusing the optical fibers are not shown in FIG. 1. However, the electrodes are fixedly secured perpendicularly to the plane of the drawing with the axes of the electrodes extending through the intersections of the line 19, that is, the left-hand surface of the stop 4, and the axes of the fibers 1 and 1'.
Upon depression of a drive start button (not shown), the reference element 4 is automatically retracted downwardly and the motor 8 is started. The rotation of the motor 8 is transmitted through the gears 7' and 7 to the micrometer head 6 rotating the micrometer head 6. The direction of rotation of the motor is chosen so that the end of the micrometer head 6 is moved backwardly. Therefore, the fixing stand 3' is moved forwardly on a sliding rail (not shown) urged by the force of the spring 5.
Simultaneously upon the start of the motor rotation, a timer is operated to effect an electrode discharge for a period of time T.sub.1 which is defined by the following equation: EQU l-VT.sub.1 =.alpha.,
where l is the width of the stop, V is the speed of the end of the fiber which is moved by the rotation of the motor, and .alpha.=10 to 50 .mu.m. After the discharge has been started, the fiber is continuously moved forwardly. However, it is stopped a period of time T.sub.2 after the discharge was started. The period of time T.sub.2 is defined by the following equation: EQU VT.sub.2 =.alpha.-.epsilon.
where .epsilon.=-5 to -50 .mu.m. The discharge is stopped a period of time T.sub.3 after it was started. At this instant, connection of the fibers has been completed. After the discharge has been stopped, the fibers thus connected are removed from the device. Thereafter, a reset button (not shown) is depressed as a result of which the motor 8 is rotated in the opposite direction and, after a period of time T.sub.4 defined by the following equation, the motor 8 is stopped: EQU VT.sub.4 =l-.epsilon..
As is clear from the above description, in the conventional technique, the speed of revolution of the motor is maintained constant to fix the above-described periods of times thereby to determine the position of the fiber. However, the conventional technique is disadvantageous in the following points. If the speed of the motor should in fact change, the fiber will be positioned inaccurately. In addition, variations in the positioning the fiber may be caused by the variations in the output of the timer.
Accordingly, an object of the invention is to eliminate the above-described difficulties accompanying the conventional technique. More specifically, an object of the invention is to position the ends of fibers with high accuracy so that the fibers can be fused together with low loss.